Heretofore olefinic compounds containing from 2 to about 4 carbon atoms were utilized as starting materials for the production of alcohols. The alcohols were conventionally produced by the hydration of the olefins using a relatively concentrated sulfuric acid solution, that is, a solution which contained more than about 55% sulfuric acid. The olefin was converted to the sulfuric acid ester in one stage and was thereafter hydrolyzed to the corresponding alcohol after lowering the acid content of the solution to less than 40%. The utilization of a relatively concentrated sulfuric acid solution to effect the hydration of the olefins possessed inherent disadvantages. For example, it is costly to concentrate the dilute sulfuric acid solution. In addition, it is well known that concentrated sulfuric acid is a dangerous chemical and therefore precautions must be taken when utilizing this chemical in order to avoid accidents which may occur. Furthermore, corrosion problems may also arise and thus would necessitate the use of relatively expensive equipment in order to efficiently produce the desired alcohol.
As will hereinafter be shown in greater detail, it has now been discovered that in contrast to the conventional process, it is possible to effect a direct hydration of the olefinic compounds in one step to produce the corresponding alcohol. This result is obtained by utilizing a dilute sulfuric acid solution of the type hereinafter set forth in greater detail and, in addition, by utilizing a transition metal sulfate it is possible to reduce any corrosion problems which may be present in the process.
This invention relates to a process for the direct hydration of olefinic compounds. More specifically, the invention is concerned with a one step direct hydration process of olefinic compounds to the corresponding alcohols by utilizing a sulfuric acid solution which is relatively direct in nature.
Alcohols constitute an important class of chemicals which find a wide variety of uses in industry. For example, one of the most common alcohols, namely, ethyl alcohol, may be used as a solvent and extraction medium, as a component in the manufacture of intermediates organic derivatives, dyes, synthetic drugs, synthetic rubber, detergents, cleaning solutions, surface coatings, cosmetics, pharmaceuticals, beverages, automobile radiator antifreeze, etc. Likewise, isopropyl alcohol is used in the manufacture of acetone, diacetone alcohol as a solvent for essential and other oils, alkaloids, gums, resins, etc., as a latent solvent for cellulose derivatives, as an antistalling agent or deicing agent for liquid fuels, in pharmaceuticals, perfumes, liquors, preservatives, rocket fuels, etc. The butyl alcohols such as n-butyl alcohol is used in the preparation of esters, as a solvent for resins and coatings, in plasticizers, hydraulic fluids, etc.; while sec-butyl alcohol may be used in the preparation of methyl ethyl ketone, and as a solvent in varnishes, lacquers, and paint removers.
It is therefore an object of this invention to provide a process for the hydration of olefins.
A further object of this invention is to provide a one step direct hydration process of olefins to the corresponding alcohols utilizing a dilute sulfuric acid solution.
In one aspect an embodiment of this invention resides in a process for the direct hydration of an olefinic compound which comprises treating said olefin with a dilute sulfuric acid solution at reaction conditions and recovering the resultant hydrated compound.
A specific embodiment of this invention is found in a process for the direct hydration of an olefinic compound which comprises treating propylene with a dilute sulfuric acid solution in which the concentration of sulfuric acid in said solution is in a range of from about 0.05 to about 40% by weight and in the presence of copper sulfate at a temperature in the range of from about 100.degree. to about 300.degree. C. and a pressure in the range of from about 1 to about 250 atmospheres, and recovering the resultant isopropyl alcohol.
Other objects and embodiments will be found in the following further detailed description of the present invention.
As hereinbefore set forth the present invention is concerned with a process for the direct hydration of olefinic compounds, and particularly olefinic hydrocarbons containing from 2 to about 4 carbon atoms in a one step process. Examples of olefins which may be subjected to the direct hydration process of the present invention will include ethylene, propylene, n-butylene and isobutylene. The hydration of the olefins is effected by treating said olefin in the presence of a dilute aqueous sulfuric acid solution in which the concentration of sulfuric acid present therein is in a range of from about 0.05 to about 40% by weight. The reaction conditions under which the hydration is effected will include elevated temperatures in the range of from about 100.degree. to about 300.degree. C. and elevated or superatmospheric pressures in the range of from about 1 to about 250 atmospheres. The superatmospheric pressure may be afforded by the autogenous pressure of the olefin which is undergoing hydration or, if so desired, the olefin may provide only a partial pressure, the remainder of the desired operating pressure being supplied by the introduction of a substantially inert gas such as nitrogen, helium, argon, etc., into the reaction vessel. In addition to the operating parameters hereinbefore discussed, the mole ratio of water to olefin constitutes another operating variable, the mole ratio of water to olefin being in a range of from about 1:1 to about 40:1 moles of water per mole of olefin.
While the hydration reaction is effected in the presence of a dilute aqueous sulfuric acid solution, it is also contemplated within the scope of this invention that transition metal sulfates may also be present in the reaction mixture. The presence of these transition metal sulfates will greatly reduce the sulfuric acid concentration level and concomitantly also reduce the corrosion problems which may be present in the reaction system. Examples of transition metal sulfates which may be employed will include copper sulfate, nickel sulfate, zinc sulfate, cadmium sulfate, cobalt sulfate, chromium sulfate, molybdenum sulfate, titanium sulfate, zirconium sulfate, vanadium sulfate, etc. It is to be understood that these metal sulfates are only representative of the class of transition metal sulfates which may be employed, and that the present invention is not necessarily limited thereto. In another embodiment of the invention it is contemplated that an aqueous solution of a transition metal sulfate of the type hereinbefore set forth may be employed as the catalyst for the hydration reaction. However, use of the transition metal sulfate per se without the presence of a dilute sulfuric acid may not necessarily result in equivalent results as pertaining to the obtention of the desired hydrated compound.
The process of this invention may be effected in any suitable manner and may comprise either a batch or continuous type operation. For example, when a batch type operation is used a quantity of the dilute aqueous sulfuric acid solution is placed in an appropriate apparatus such as an autoclave of the rotating, mixing or stirring type. In addition, an added amount of water may also be placed in the autoclave to bring the desired molar ratio of water to hydrocarbon within the desired range. The autoclave is then sealed and the olefinic hydrocarbon which is to be hydrated is charged thereto along with any inert gas, if so desired, until the desired initial operating pressure has been reached. The autoclave is then heated to the predetermined operating temperature and maintained thereat for a period of time which may range from about 0.05 up to about 10 hours or more in duration. Upon completion of the reaction time the autoclave and contents thereof are allowed to return to room temperature, the excess pressure is discharged and the autoclave is opened. The reaction mixture is recovered therefrom and subjected to conventional means of separation which may include extraction, fractional distillation, etc., whereby the desired alcohol is separated from any unreacted starting material and/or side products which may have formed during the reaction and recovered.
It is also contemplated within the scope of this invention that the hydration reaction may be effected in a continuous manner. When such an operation is to be used the olefin and water along with any dilute aqueous sulfuric acid solution is charged to a reactor which is maintained at the proper operating conditions of temperature and pressure. After remaining in the reactor for a predetermined period of time, the effluent is continuously withdrawn and passed to a separation stage wherein the products are separated from any unreacted olefin, said unreacted olefin being recycled to the reaction zone to form a portion of the feed material. The bottoms from the separator which comprise the desired alcohol along with any side reaction products such as oligomers or ethers are then subjected to a distillation in an extraction column, said extraction being effected in the presence of an azeotropic solvent such as benzene, paraffins, olefins, etc., whereby the desired product may be separated from the aforesaid side reaction products and recovered.